One very active research tradition in the field of second language acquisition (SLA) attempts to establish causal relationships between environmental factors and learning. These include the type and quantity of input, instruction and feedback, and the interactional context of learning (Larsen-Freeman and Long 1991). A second very influential line of research and theory in SLA that came to fruition during the 1980s investigates the possible role of universal grammar (UG) in SLA (Eubank 1991b, White 1989). In the Chomskyan tradition, UG refers not to properties of language as the external object of learning but to innate properties of mind that direct the course of primary language acquisition. One question asked within this tradition has been whether or not second language learners still “have access” to UG, but it is assumed that UG principles are not accessible to learner awareness for any kind of conscious analysis of input. It is possible that SLA is the result of UG (a deep internal factor) acting upon input (an external factor), as proposed by White (1989), but what seems to be left out of such an account is the role of the learner's conscious mental processes.